1. Field of the Invention
The present invention relates to a pixel structure and thin film transistor and fabrication method thereof. More particularly, the present invention relates to a thin film transistor with a source and a drain made of metallic material and a pixel structure having the thin film transistor and the fabrication method thereof.
2. Description of Related Art
The rapid development of multi-media in our society comes as a result of the many advances in the technology for manufacturing semiconductor and display devices. For display device, thin film transistor liquid crystal display (TFT-LCD), with its high display quality, high spatial utilization, low power consumption and radiation-free operation, has gradually become one of the mainstream products in the market. In fact, thin film transistors have been commonly used inside the thin film transistor liquid crystal display.
FIG. 1 is a schematic cross-sectional view of a conventional thin film transistor. As shown in FIG. 1, the conventional thin film transistor 100 includes a substrate 110, a channel layer 120, a source 130, a first metal contact layer 130a, a drain 140, a second metal contact layer 140a, a gate insulation layer 150, a first dielectric layer 152 and a gate 160. The channel layer 120 is disposed on the substrate 110 and the source 130 and the drain 140 are disposed on the respective sides of the channel layer 120. The gate insulation layer 150 covers the channel layer 120, the source 130 and the drain 140. The gate 160 is located on the gate insulation layer 150 above the channel layer 120. The first dielectric layer 152 covers the gate insulation layer 150 and the gate 160. Furthermore, the first metal contact layer 130a and the second metal contact layer 140a are electrically connected to the source 130 and the drain 140 via the contact opening P1 and P2 respectively.
Conventionally, the channel layer 120, the source 130 and the drain 140 are fabricated using the following steps. First, a polysilicon layer (not shown) is formed over the substrate 110. After forming a gate 160 on the polysilicon layer, an ion implantation is carried out using the gate 160 as a mask to form the source 130 and the drain 140 in the polysilicon layer. Because the source 130 and the drain 140 are formed in an ion implantation, the production requires a longer time and a higher cost. Moreover, the source 130 and the drain 140 made of polysilicon material, and the first metal contact layer 130a and the second metal contact layer 140a for electrically connecting with the source 130 and the drain 140 are made of a different material. As a result, the contact resistance between the source 130 and the first metal contact layer 130a and the contact resistance between the drain 140 and the second metal contact layer 140a are high. When the dimension of the liquid crystal display panel increases in the future, the foregoing high contact resistance will cause more resistance-capacitance delay in signal transmission. Ultimately, the display quality of the liquid crystal display panel will be compromised.